Many high temperature films of aromatic polymers such as polyamide, polyimide, polyester and polysulfone are commercially produced or widely investigated to overcome the mediocre heat resistance of polyethylene terephthalate film, the most commonly used high performance industrial film. However, their poor mechanical properties as well as their economic disadvantages prohibit the wide use of these films in many applications, especially in the electrical industry.
Polyphenylene sulfide has been known as a thermoplastic polymer with a melting point of 280.degree. to 290.degree. C., which inherently has excellent resistance to high temperature and chemicals such as organic solvents, acids and bases. Films of polyphenylene sulfide may therefore be prepared by extruding the molten polymer through a narrow orifice and chilling the polymer in film form. Polyphenylene sulfide is now commercially produced by Phillips Petroleum Company with a trademark of "RYTON". However, "RYTON" is a resin originally for powder coating and injection molding, and from this polymer only impractical films with poor surface roughness, inferior mechanical properties and poor thermal stability can be obtained. No information of any significance is available relating to films of poly-p-phenylene sulfide, because of the difficulty in obtaining the inherent remarkable properties of poly-p-phenylene sulfide in practical films.
An object of the present invention is to provide a poly-p-phenylene sulfide film having an outstanding combination of physical, chemical and electrical properties which is industrially advantageous for various applications. Other objects will be apparent from a further description of the invention hereinafter.